What is Epidermal Inclusion Cyst?
Epidermal inclusion cysts, also known as epidermoid cysts, epidermal cysts, infundibular cysts, inclusion cysts, or keratin cysts, are the most common types of skin cysts. They can appear anywhere on the body and generally appear as small lumps directly under the skin, often with a visible central point. These cysts are usually mobile and can range in size from a few millimeters to several centimeters across.
These cysts may not change or may gradually get bigger over time. It’s hard to predict whether a cyst will grow, become inflamed, or remain unchanged. Inflamed or fluctuating (fluid-filled) cysts tend to be larger, redder, and more noticeable to the person. These cysts can become painful due to the body’s inflammatory response and may appear as a fluctuating lump under the skin.
Inside this type of cyst, there’s generally keratin, not sebum (oil produced by our skin). Keratin often looks “cheesy.” These cysts do not come from sebaceous (oil) glands, so they’re not sebaceous cysts. However, people often mistakenly use the term “sebaceous cyst” to refer to what’s technically an “epidermoid cyst.”
What Causes Epidermal Inclusion Cyst?
Most epidermoid cysts happen randomly. These cysts are very common, harmless, not infectious, and can seem to disappear by themselves. But without proper treatment, they can come back. They frequently show up in areas that have inflamed hair follicles and often appear alongside acne.
Risk Factors and Frequency for Epidermal Inclusion Cyst
Epidermal inclusion cysts, or epidermoid cysts, are more commonly seen in men than women, at a ratio of 2:1. These cysts are especially frequent in individuals in their 20s to 40s. Generally, these cysts are not inherited, but in certain rare conditions like Gardner syndrome, nodular elastosis with cysts and comedones (Favre-Racouchot syndrome), and basal cell nevus syndrome (Gorlin syndrome), they can be passed down from generation to generation.
Older adults with sun-damaged skin have a higher chance of developing these cysts. Similarly, people using BRAF inhibitors, such as imiquimod and cyclosporine, are more likely to develop these cysts on their face.
Epidermal inclusion cysts often develop in areas where the hair follicles have been inflamed or irritated repeatedly. They are more prevalent in people suffering from a common skin condition known as acne vulgaris. Interestingly, these cysts can also be seen in newborns, a condition referred to as milia.
Signs and Symptoms of Epidermal Inclusion Cyst
Epidermoid cysts are typically diagnosed through physical examination. The recognizing features include a round and movable lump under the skin, which may have a visible center point. These cysts can appear anywhere on the body and are noticeable as bumps right below the surface of the skin. The size of these cysts can vary from tiny (a few millimeters) to quite large (several centimeters). Some cysts might stay the same size, while others might grow larger over time. It’s impossible to predict whether a cyst will grow, become inflamed, or remain unchanged. If a cyst gets infected, it might appear larger and more red, making it more noticeable to the patient.
If inflammation occurs, it could lead to the rupture of the cyst and the leaking of the cyst contents into the nearby skin or underneath the skin tissues. This rupture might or might not result from an active infection. The usual sources of infection in cysts come from bacteria that normally live on the skin, such as Staphylococcus aureus and Staphylococcus epidermidis. Epidermoid cysts usually don’t cause any symptoms unless they rupture.
Testing for Epidermal Inclusion Cyst
Epidermoid inclusion cysts, which are small, benign lumps under the skin, are usually assessed by doctors during a regular office visit by asking you about your symptoms and examining the cysts. Generally, there isn’t a need for a deeper examination of the cyst’s structure before removal in surgery. Tests like ultrasounds or lab work, used to create images or check for particular conditions, are not usually required. Your doctor would only order these if they suspect you may have a genetic condition linked to the cysts based on their evaluation.
Treatment Options for Epidermal Inclusion Cyst
If you have an inflamed but non-infected epidermal inclusion cyst (a buildup of skin tissues), it’s unlikely to get better on its own without treatment or surgery. Typically, treatment isn’t urgent unless you’re experiencing severe symptoms like pain and infection, or you decide to treat it before it worsens.
The most effective way to treat an epidermal inclusion cyst is to surgically remove it. Sometimes, a less invasive therapy alternative is used, involving an injection into the inflamed cyst. This can reduce inflammation, prevent infection, and might decrease the need for a surgical procedure to drain the cyst.
Detailed surgical removal of the cyst, leaving no parts behind, is the only sure way to prevent its recurrence. This type of surgery is easier to perform and more likely to be successful if the cyst isn’t severely inflamed. That’s because inflammation makes the cyst wall fragile and blurs the surgical lines, complicating the full removal of the cyst and increasing the chance of recurrence.
The surgery is performed under local anesthesia, meaning you’ll be awake but won’t feel any pain. A small incision is made on your skin, on top of the cyst. The contents of the cyst are then squeezed out by applying pressure on either side of the incision. The cyst’s wall is often extracted from the surrounding tissues and removed in its entirety through the small incision. This technique, known as minimal incision, leaves less visible scars compared to standard surgical techniques. The recurrence rates of the cyst with this technique range from 1% to 8%. To achieve better cosmetic results, the skin is carefully stitched back together in multiple layers.
An alternative method involves using a specialized tool (4 mm punch biopsy) to create a small hole and extract the cyst intact. Regardless of the approach taken, it is crucial to remove the entire cyst to prevent it from growing back.
If the cyst has turned into a swelling filled with fluid, it may need to be lanced and drained, and lumps inside the cyst destroyed. If there’s an infection around the cyst, you may be prescribed oral antibiotics. In some cases, the cyst is drained, the patient is given antibiotics, and the remaining cyst is surgically removed later on. This last step is important because without surgery, the cyst is very likely to recur.
What else can Epidermal Inclusion Cyst be?
When a doctor suspects an epidermoid inclusion cyst, they must consider various other conditions that might resemble it, such as:
- Pilar cyst
- Lipoma
- Abscess
- Neuroma
- Benign growths
- Skin carcinomas
- Metastatic cutaneous lesions
- Pilomatrixoma
- Ganglion cyst
- Neurofibroma
- Dermoid cyst
- Brachial cleft cyst
- Pilonidal cyst
- Calcinosis cutis
- Pachyonychia congenita
- Steatocystoma simplex
- Steatocystoma multiplex
The doctor will need to carefully consider these possibilities in order to accurately diagnose the condition.
What to expect with Epidermal Inclusion Cyst
The outlook is very good for people who have epidermal inclusion cysts, as long as the entire cyst, including the contents and the wall that surrounds it, is completely removed.
Possible Complications When Diagnosed with Epidermal Inclusion Cyst
Epidermal inclusion cysts can have complications before they are definitively treated. These can be triggered by the cyst bursting, leading to symptoms like redness, pain, swelling, and localized skin infection. One frequent issue in medicine is the cyst coming back, especially if it wasn’t fully removed during surgery.
Like all surgeries, there’s always a small chance of complications. For epidermal inclusion cyst removals, this could include infection, bleeding, harm to nearby structures and tissues, scarring, and the surgical wound reopening.
There’s also a chance the cyst could reappear if the entire capsule isn’t completely removed during surgery.
Side Effects: Complications to look out for:
- Redness
- Pain
- Swelling
- Localized skin infection
- Infection after surgery
- Bleeding
- Damage to surrounding body parts and tissues
- Scarring
- Surgical wound reopening
- Cyst recurrence
